Field of Invention
The present invention relates to a package substrate and a manufacturing method of the package substrate.
Description of Related Art
A package substrate is used to support an integrated circuit (IC) die and is referred to as a carrier. The package substrate has inner lines and electrical contacts, such that the electrical contacts on two opposite sides of the package substrate can respectively electrically connect to the semiconductor die and a printed circuit board (PCB). As a result, the semiconductor die and the PCB may transmit signals through the inner lines of the package substrate. With the development of semiconductor manufacturing technology, designers demand increasingly higher standards with respect to wire layout density, transmission speed, and signal disturbance, and thus package substrates have been extensively utilized in electronic products. For example, package substrates may be used in smartphones, tablet computers, network and communication solutions, laptop computers, etc.
In manufacturing a typical package substrate, a patterned conductive layer is formed on a carrier, such that the conductive layer has openings that expose the carrier. Thereafter, a copper pillar layer is formed on the conductive layer, and a dielectric layer is utilized to cover the conductive layer and the openings. As a result, after the carrier is removed, the entire conductive layer is exposed. However, only a portion of the conductive layer is utilized to electrically connect to a semiconductor die. If the conductive layer is directly connected to the electrical contacts of the semiconductor die, they will be easily separated due to the poor bonding force therebetween, thereby reducing reliability. In order to improve the bonding force between the package substrate and the semiconductor die, a nickel layer and a gold layer are often electroplated on the conductive layer. However, due to process limitations, the nickel layer and the gold layer are formed on the entire exposed conductive layer, and cannot be formed only on portions of the conductive layer corresponding to the electrical contacts of the semiconductor die. Therefore, the cost of the package substrate may be significantly increased.